<select name="{{ widget.name }}"{% include "django/forms/widgets/attrs.html" %}>{% for group_name, group_choices, group_index in widget.optgroups %}{% if group_name %}
<optgroup label="{{ group_name }}">{% endif %}{% for option in group_choices %}
    {% include option.template_name with widget=option %}{% endfor %}{% if group_name %}
</optgroup>{% endif %}{% endfor %}
</select>
<script>django.jQuery('#id_{{widget.name}}').select2()</script>